Various chemical and industrial processes produce phenol-containing waste waters which are toxic to the environment and from which the phenols must be removed prior to disposal.
For example, phenol-containing waste waters are produced by the scrubbing or condensation of the gases derived from cokefication plants in which coke is produced for use in metallurgical industries, from coal-gassification plants and from a variety of chemical processes and other industrial plants. The phenol-containing waste waters may derive, as noted, from a scrubbing process or simply from the condensation of the gases produced in coke-burning, coal-burning and like combustion or thermal degradation reactions.
Dephenolation, i.e. the removal or recovery of phenol, from such waste waters can be affected in a variety of ways in accordance with teachings in the art. For example, it is known to dephenolate waste waters by a biological degradation of the phenol content thereof in synthetic biological environments and installations.
Alternatively, phenols can be removed by extraction or scrubbing with selective organic solvents, by steam distillation, or by adsorption on materials having a high surface activity, including active carbon, silica gel and synthethic-resin exchangers.
Depending upon the process and the phenol concentration of the waste water, the phenol can be recovered or the level of phenols in the waste water can be reduced to a negligible degree. In most cases, however, a recovery of the phenols is not practical since the expense for such recovery renders a process in which recovery is contemplated relatively impractical. Furthermore, the cost for phenol recovery from solvents or adsorbents is often excessive.
In the adsorption process, practical considerations have limited the adsorbent to active carbon.
An adsorption process for the removal of phenols from waste waters, using active carbons, has various problems associated with it. For example, apart from the phenols, there are other constituents of the waste water deposited upon the active carbon and cannot be removed readily therefrom. Such materials include resinous and asphalty materials. In addition, the desorption or regeneration process have a tendency to produce resinous and asphalty materials which are not completely released or destroyed in the active carbon so that the active carbon must be replaced more than is economically feasible and cannot be reused to the desired degree. Notwithstanding these disadvantages, a treatment of the active carbon for reuse is practically mandated by the high cost of the adsorbent.
One of the ways which has been proposed in order to increase the economy of active-carbon adsorption processes for the dephenolation of waste waters requires a pretreatment of the waste waters to remove the oily and tarry components thereof.